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65
votes
4answers
7k views

Where does the extra kinetic energy come from in a gravitational slingshot?

I read in this answer in this site that the KE a free-falling ball acquires is not originated by the attracting body but that energy was actually stored in the ball when it had been lifted to the ...
41
votes
4answers
8k views

If I'm floating in space and I turn on a flashlight, will I accelerate?

Photons have no mass but they can push things, as evidenced by laser propulsion. Can photons push the source which is emitting them? If yes, will a more intense flashlight accelerate me more? Does ...
36
votes
6answers
42k views

Could someone jump from the international space station and live?

Felix Baumgartner just completed his breathtaking free-fall skydiving jump from $120,000\,\text{feet} = 39\,\text{km}$ above the Earth, breaking the speed of sound during the process. I was wondering ...
29
votes
1answer
7k views

How long would it take me to travel to a distant star?

Suppose I wanted to travel to one of the recently discovered potentially Earth-like planets such as Kepler 186f that is 490 light years away. Assuming I had a powerful rocket and enough fuel, how long ...
24
votes
8answers
6k views

Why don't modern spacecraft use nuclear power?

The Voyager 1 & 2 spacecraft launched in 1977 with Plutonium as their source of electricity. 34 years later they claim these two spacecraft have enough power to last them until at least 2020. That ...
16
votes
4answers
970 views

How would we see a near-lightspeed object emitting light?

Consider an object travelling near the speed of light relative to us (let it be a spaceship or a star), which is emitting light (consider it monochromatic resulting from a two level electronic ...
14
votes
4answers
425 views

Why are spacecraft made to “spin” after launch?

At some point after launch, usually just before or after separation from the last booster stage, spacecraft are often made to "spin" (about the axis of their trajectory)? See e.g this You Tube video. ...
12
votes
2answers
104 views

How are interplanetary trajectories found?

How are interplanetary trajectories that involve gravity assist maneuvers found? Examples: the MESSENGER spacecraft made flybys of Earth, Venus, and Mercury before getting into orbit the Juno ...
11
votes
2answers
2k views

How fast would a spaceship have to go to reach Alpha Centauri within a person's lifetime?

Given the recent news about the discovery of an "Earthlike" planet orbiting Alpha Centauri (our nearest stellar neighbour) it got me wondering just how fast would spaceship have to travel to be able ...
8
votes
2answers
387 views

What exactly is the composition of radiation in interplanetary space?

The articles I found on radiation in the solar system mostly dealt with solar wind, I wonder about other types. Is there a breakdown that tells me, withhin an order of magnitude, at least what ...
8
votes
1answer
319 views

Graphene as optical and UV mirrors

One usually hears about graphene as a good thermal conductor, and good light absorber due to its tunable bandgap properties. But i haven't heard about its aplicability as an optical mirror. In fact, ...
7
votes
1answer
364 views

Antimatter Propulsion System

Is there a possibility ( in theory ) to build a antimatter propulsion system, if so how can we control the collision of matter-anitmatter, will humans be able to control this force just like ...
7
votes
2answers
630 views

How would one navigate interstellar space?

Headed out from Earth within the Solar System, Sol and Earth both may be used as reference. When traveling in interstellar space with stellar systems themselves traveling at varying velocities even ...
7
votes
6answers
5k views

How close can spaceship get to the Sun

If you want to fly a spaceship with human passengers as close to the Sun as possible, then what effects would the spaceship have to be designed to counteract in order to keep the passengers alive and ...
6
votes
5answers
8k views

Why can't a spaceship accelerate for ever? Since there is no friction in space

I have seen many answers like: because we don't have infinite energy, because of gravity, because it is impossible, because of physics. But they don't really answer my question.. I mean if there is ...
6
votes
6answers
1k views

What are the most realistic ways of high speed space propulsion?

Liquid and solid chemical fuels in rockets are very expensive and inefficient. I have heard of solar sails but what are the most realistic space travel fuels that will be used in the future to get ...
6
votes
3answers
467 views

Would approaching a distant star at near the speed of light unfold its entire history in “fast-forward”?

The light we detect today in our telescopes from distant stars is really old. If we could travel fast (lets say, 90% the speed of light) towards a star a million lightyears away, all the time looking ...
6
votes
1answer
448 views

Movie Interstellar - Question about Escape Velocity

The movie Interstellar shows people on a water planet where time is dilated so much that 1 hour is equal to 7 years back on Earth. Even though they lift off from Earth using a Saturn-V two stage ...
6
votes
2answers
277 views

Physics and math behind flight through solar system: Where to start?

I wrote a first program that simulates a solar system. I was able to calculate the locations for every planet on its elliptical route for any given time. In a second program i managed to simulate ...
5
votes
3answers
2k views

Is interstellar flight possible in near future in a way that would keep our civilization alive?

Is interstellar flight possible in the near future in a way that would keep our civilization alive? I mean is it practically possible to obtain technology that would enable us to travel to nearby ...
5
votes
1answer
307 views

Travel duration from Earth to a star at 9.8 m/s² acceleration

How much time would it take for a traveler (in traveler's perspective) to reach a star at distance $d$, if it accelerates at 9.8 m/s² (for a comfortable travel)? I understand that $V = V_0 + a\times ...
5
votes
3answers
4k views

How do they produce air on the ISS?

How do they provide air on the ISS? I know it is produced by electrolysis but is that all they breathe, hydrogen and oxygen? The air here on Earth contains other things like nitrogen. Do the people ...
5
votes
2answers
1k views

What is the fastest a spacecraft can get using gravity-assist?

Assuming normal spacecraft and space objects (no neutron stars, black holes, etc). To what speed can a spacecraft accelerate using gravity-assist? For example, if a spacecraft is moving at ...
5
votes
3answers
1k views

What Problems for 50 year space probe to Alpha Centauri?

I'm thinking speculatively. NASA is doing experiment with ion thrust tech. Assuming, that inside the next 5 years, we could create a probe which would take on the order of 30 to 50 years to reach ...
5
votes
2answers
635 views

What properties would the ideal material for spacecraft construction possess?

Assuming we develop the capability to send a robot to study Gliese 518, or any of the Earth-like planets discovered in the neighbourhood; the spacecraft would need to travel through the Solar System ...
5
votes
1answer
506 views

Finding interplanetary flight trajectory using calculus of variations?

Consider two orbits $x(t),\space y(t)$ representing the origin and destination for some spaceflight of interest. These could be, for example, cycloids describing LEO and another orbit circling, say, ...
5
votes
0answers
97 views

What is the cheapest way to land a grain of sand on the moon? [closed]

I have a payload that is the size and density of a grain of sand. I want to land it intact on the moon, but I am not particular about location beyond that. What is the least expensive way to get it ...
4
votes
1answer
75 views

Relativistic Time dilation and travel to exoplanets

NASA recently discovered the first habitable exoplanet with the Kepler space telescope. Recently I was on this site: http://www.cthreepo.com/lab/math1/ With the Long Relativistic Journeys ...
4
votes
2answers
246 views

Are we going to be able to travel trough space deforming the space-time?

I'm not talking about the speed of the spaceship. If we can deform space-time we needn't any type of propulsion. And how can the travel affect to it's pilots? Can they survive?
4
votes
2answers
1k views

What kind of cooling mechanism could be used in outer space?

This question arises out of this question on Quora - Apollo 11: 1969 Moon Landing: Did Neil Armstrong really land on the moon? I'm convinced with most of the explanations provided in the first ...
4
votes
3answers
224 views

Magnetic Levitation For Space Travel

At 1 G, we feel at home. At 5 G's, normal people can stay awake. At 9 G's, trained pilots with G-suits can stay awake. At 25 G's, R.I.P. Unfortunately, these numbers are limiting for space travel, ...
4
votes
0answers
140 views

What can be the lightest possible moon launch vehicle? [closed]

I tried calculating this, but it gets too complicated. Assume, we have a Moon orbit station and ISS on Earth orbit. We have a Moon base. We want to send a tourist for a week on the Moon and back. We ...
3
votes
2answers
120 views

What is stopping us from stick building a space station?

I want to understand why we do not build space stations in a similar way that we build a home, piece by piece. Instead we construct modules on the ground and fly them up. Are there some technical ...
3
votes
3answers
1k views

Why does the speed of the propellant limit the speed of a space ship in open space?

Isn't speed a relative thing in space? If so, why would the speed of a propellant matter? Why can't a space ship accelerate infinitely?
3
votes
5answers
5k views

If a space ship accelerated constantly, would its astronauts constantly feel the forward movement?

I know that if a space ship suddenly traveled very fast, its astronauts would be fly against the back wall, potentially getting hurt. If the space ship suddenly stopped, they would also fly against ...
3
votes
2answers
174 views

Orbit reversal in a gravitational well

A friend recently asked me this, and without wishing to spend a huge time thinking about it, I wondered if anyone knew the answer (or at least had an informed guess), or was familiar enough with these ...
3
votes
1answer
169 views

What's wrong with this reactionless drive?

I think this is analogues for the Woodward effect, but macroscopic: We assume a spacecraft consisting of a broomstick, a donut and lots of gear for storing and transfering mechanical energy. Take the ...
3
votes
1answer
136 views

Why does the Cassini probe experience jerky acceleration in deep space?

I was looking at this plot of speed over time for the Cassini probe. What's going on at the right, after mid-2004? Why does it keep slowing down and speeding up again?
3
votes
1answer
99 views

Burning fuel in space while accelerating and deaccelerating

Is it true that for acceleration in space we need not the same quantity of the fuel than during the deacceleration stage?
3
votes
1answer
152 views

Mars Circular Intercept Orbit

I've been trying to simulate a spacecraft entering a circular capture orbit about Mars using Mathematica, but am having a little trouble. The simulation starts when the spacecraft enters Mars' sphere ...
3
votes
0answers
169 views

Can flux pinning be used for propulsion in Earth's magnetic field?

I was wondering if the following steps would result in a net displacement on a spacecraft operating in Earth's magnetic field: Turn on a superconductor Use a linear actuator to shift some mass Turn ...
2
votes
1answer
831 views

Questions after watching the movie Interstellar [closed]

Awesome movie, but as a physics student, some questions do crop up When they travel to the watery planet, they say that 1 hour on this planet is 7 yrs om earth. How is this possible? Is the planet ...
2
votes
4answers
144 views

Conservation of potential energy for a wormhole

So you managed to build a stable traversable wormhole. Somehow you managed to acquire the exotic negative-tension materials with sufficient densities to make it all work. Now you place opening A of ...
2
votes
4answers
131 views

How much could one slow down aging using existing spacecraft?

Imagine that I board a spacecraft and head away from the Earth at top speed until I've aged twenty years, then I turn around and come back. How much younger will I be than the unexciting folk who hung ...
2
votes
3answers
1k views

Spaceships travelling through space and debris

How can a spaceship travel through space if there is space debris flying around at very high speeds? Wouldn't even a small rock crack through the spaceship?
2
votes
1answer
284 views

light absorbing diodes characteristics

Recently, there was a publication regarding some new materials that would let thru light in one direction and either absorb it or reflect it in the other direction; the publication does not clarify on ...
2
votes
1answer
658 views

How does Lunar Orbit Injection (LOI) work?

Just what the title states. I read that LOI was used by the Apollo program (and possibly others) to achieve escape velocity. How does it work? Is it merely a matter of centrifugal/centripetal force?
2
votes
1answer
129 views

Term for “atmospheric ricochet” due to wrong “angle-of-attack”

I watched "Apollo 13" yesterday, and they had the "angle-of-attack" problem that had to be manually solved, to prevent the ship from "ricochet[ing] off the atmosphere like a rock skipping off a pond". ...
2
votes
2answers
383 views

What equations do I use to do basic time dilation problems?

I understand the concepts of relativity, but I don't know where to go to set up equations to do any actual calculations. For example, what equations would I use to find out the following: A ship ...
2
votes
1answer
30 views

How can solar sails be maneuvered?

Photons from the Sun are always radial to it and hence solar sails can only travel radially. Any techniques related to maneuvering?